TY  - JOUR
AB  - Background: Environmental pH stress constitutes a limiting factor for S. meliloti survival and development. The
response to acidic pH stress in S. meliloti is versatile and characterized by the differential expression of genes
associated with various cellular functions. The purpose of this study was to gain detailed insight into the participation of sigma factors in the complex stress response system of S. meliloti 1021 using pH stress as an
effector.
Results: In vitro assessment of S meliloti wild type and sigma factor mutants provided first evidence that the sigma
factor RpoH1 plays a major role in the pH stress response. Differential expression of genes related to rhizobactin
biosynthesis was observed in microarray analyses performed with the rpoH1 mutant at pH 7.0. The involvement of
the sigma factor RpoH1 in the regulation of S. meliloti genes upon pH stress was analyzed by comparing timecourse
experiments of the wild type and the rpoH1 mutant. Three classes of S. meliloti genes could be identified,
which were transcriptionally regulated in an RpoH1-independent, an RpoH1-dependent or in a complex manner.
The first class of S. meliloti genes, regulated in an RpoH1-independent manner, comprises the group of the
exopolysaccharide I biosynthesis genes and also the group of genes involved in motility and flagellar biosynthesis.
The second class of S. meliloti genes, regulated in an RpoH1-dependent manner, is composed of genes known
from heat shock studies, like ibpA, grpE and groEL5, as well as genes involved in translation like tufA and rplC.
Finally, the third class of S. meliloti genes was regulated in a complex manner, which indicates that besides sigma
factor RpoH1, further regulation takes place. This was found to be the case for the genes dctA, ndvA and smc01505.
Conclusions: Clustering of time-course microarray data of S. meliloti wild type and sigma factor rpoH1 mutant
allowed for the identification of gene clusters, each with a unique time-dependent expression pattern, as well as
for the classification of genes according to their dependence on RpoH1 expression and regulation. This study
provided clear evidence that the sigma factor RpoH1 plays a major role in pH stress response.
DA  - 2010
DO  - 10.1186/1471-2180-10-256
LA  - eng
IS  - 1
PY  - 2010
SN  - 1471-2180
T2  - BMC Microbiology
TI  - The role of sigma factor RpoH1 in the pH stress response of Sinorhizobium meliloti
UR  - https://nbn-resolving.org/urn:nbn:de:0070-pub-19038751
Y2  - 2024-11-22T09:42:52
ER  -